Dr Andrew A. Adams #FBPE 🔶1d ago
ClaudioM

OK, so to all of the #MARCHintosh and #Macintosh retro folks out there, I need some help.

I unplugged what I believe it the main ribbon that powers the logic board of this Power Macintosh G4 "Sawtooth." After plugging it back in and attempting to turn it on, I noticed that the fan ATTEMPTS to spin, but then stops. Does that mean that my PSU has an issue and needs to be replaced?

Any help is appreciated, as well as boosts on this. ​

Mar 29 at 1:16amWeb
Show threadtheirongiant1d ago
@claudiom - I feel like this story is missing something. You just ... unplugged it and reconnected it? What were you working on inside the Mac?
Show threadClaudioM1d ago
@theirongiant I was checking to see why it wouldn't turn on at all. I guess the part that's missing is that when I opened it up and removed the power connector to the logic board and plugged it back in and turned it on, the fan tried to spin but stopped.
Show threadtheirongiant1d ago

@claudiom - Was it working at one point? When did it stop working?

Also, which Sawtooth variant do you have: PCI, AGP, Digital Audio, or Gigabit Ethernet?

Show threadClaudioM1d ago
@theirongiant This is the AGP one from what I can tell. I got this from my cousin's husband years ago, and it never worked since I got it now that I remember. It was free, and he didn't know why it stopped turning on, so I took it anyway.
Show threadtheirongiant1d ago
@claudiom - try the troubleshooting steps in the repair manual, beginning on page 203 of the PDF. Try resetting the PMU as described on pages 209-212. Also test that the battery has sufficient voltage. Manual here: http://www.applerepairmanuals.com/the_manuals_are_in_here/PowerMac_G4.pdf
Show threadClaudioM1d ago
@theirongiant I've pulled the PRAM battery to prevent leakage on the logic board as I lost a IIgs logic board because of that. ​ Supposedly, it _should_ boot even without the PRAM battery. I've already pushed the PMU button, and it hasn't worked. I'll have to find the time in the future to open up that PSU and see if a cap or caps has/have gone bad.
Show threadtheirongiant1d ago
@claudiom Try putting the battery back in temporarily. Some macs were weird about booting without a battery present. Leakage happens during long term storage, not suddenly.
Show threadClaudioM21h ago
@theirongiant Yeah, that I know, but from what I've read, this one should boot up without a PRAM battery. IIRC, it still would t boot even when it had the battery, but I'll test this week nonetheless.
Show threadtheirongiant1d ago
@claudiom - also, read a bit further in the manual. There is information for testing and validating the voltages from the PSU and on the board.
Show threadClaudioM1d ago
@theirongiant Just downloaded the PDF to use in the future. Thanks!
Show threadMiguel Arroz1d ago
@claudiom I had that exact problem in a PowerMac G5. The PSU passed the simple test described on the Apple Service Manuals (had voltage on a specific pin) but when I turned it on, the fans would shake a little, and that was it. Turned out to be a bad PSU. It was replaced and the machine now works without issues.
Show threadMiguel Arroz1d ago
@claudiom Still, before you start working on the PSU or finding a replacement, disconnect/remove anything you can from the Mac. Disks, DVD drive, PCI/AGP cards (including the graphics card), memory, etc. Leave just the minimum number of memory modules you need for the machine to boot in the correct slots (I believe in that machine it’s two, in a pair? Check it out, I may be misremembering) and see if it works. There may be something shorted forcing the PSU to turn off.
Show threadClaudioM1d ago
@arroz Thanks for the tip. I'll do exactly that, and hope that resolves the issue. Otherwise, I may be looking for a replacement PSU as you did.
Show threadMiguel Arroz21h ago
@claudiom If you feel comfortable with that try recapping the PSU. Might just be some caps leaking.